Q u o t e: Well with the change to armor to damage reduction instead of reducing chance to be hit, a "to hit" stat doesn't make a whole lot of sense. It would just be a stat that you put X amount of points into to hit cap, and then ignored. Not interesting or fun.
To be fair, that's the point of the stat. It adds a bit of... I don't want to say strategy because it's not quite that, but that's the only word I can think of. Anyway, it adds a bit of strategy to acquiring stats.
With the hit stat you cant just go ahead and equip that new chestpiece that's all full of power and haste rating, you have to take into account that you'll lose that 6% to hit that you currently have on your armor. This makes gearing up slightly more challenging and thought-provoking.
However, in my opinion, Diablo does not really absolutely need it. It's more noticeable in a game like WoW where you have encounters that require deep strategy and clear skill rotations during the whole 7 minute fight. It's during those long encounters that you can actually notice a 2% miss chance. Diablo 3 promises faster paced, more dynamic styles of enemy encounters where that sort of thing will matter less and less, especially with the types of skills that we now see and the more active role they play.